1. Field of the Invention
The invention, in general, relates to an apparatus for connecting polymeric tapes or the end portions thereof by heat welding and, more particularly, to an apparatus of the kind provided with a tongue-shaped or cantilevered temperature controlled welding head mounted on a pivotable arm.
2. The Prior Art
For purposes of reducing their weight as well as to prevent their rupture during transport, packing materials such as, for instance, crates, boxes and the like are often tied together or secured by polymeric ribbons or tapes. It is important that the tapes are tautly drawn and that their ends are securely connected. Furthermore, when packaging large quantities of items it is also important that the cycle times for tying or taping the boxes be as short as possible.
Commonly used polymeric packing tapes or ribbons may be securely connected by heat-welding or fusing and pressing. Relatively large heating device are required nowadays for heating the connecting spots. Such devices tend to be expensive as a result of their structural complexity as well as high power consumption. Heat dissipation in particular leads to power losses and heating of machine components. In addition, their heavy weight mitigates against convenient insertion of their welding head between the tapes at the connecting spot thereof.
It is, therefore, an object of the invention to provide a simplified and compact apparatus for forming localized connections between polymeric tapes.
Another object is to provide a compact apparatus for heat connecting polymeric tapes which is of low structural complexity and low power consumption.
Yet another object is to provide a tape welding apparatus of the kind which quickly reaches a stable operating temperature.
In the accomplishment of these and other objects the invention provides for a tape welding apparatus provided with a welding head and thermostat housed in a flat tube and associated with means disposed on the pivot arm ahead of the welding head for controlling the heat thereof.
A welding head structured in this fashion may be pivoted directly between tapes to be connected control module for heating the connection spot. To this end the heat of the welding head may be controlled such that it corresponds to given requirements even at short cycle times for taping up large numbers of boxes in the shortest possible time. Heat and energy losses are very low since heat is only generated where it is required for welding the tape.
By comparison with conventional equipment of this kind in which the temperature control is remote from the welding head and connected therewith by a highly flexible and expensive connecting cable, the apparatus in accordance with the invention is provided with a heat control module rigidly connected to the welding head. Possible defects in the transmission of very low user voltages in the millivolt range of the thermostat are thus effectively prevented.
In an advantageous embodiment the invention the control module is connected to a source of voltage and to the welding head and thermostat, and a potentiometer is provided for controlling the temperature of the welding head. The control module may be very compact and for the feed voltage it requires but a simple and cheap cable.
In accordance with a further embodiment, the control module controls the temperature as a function of the voltage. In this manner, voltage fluctuations cannot lead to temperature fluctuations of the welding head.
In yet another advantageous embodiment of the invention the thermostat for detecting the heating temperature is mounted between insulating materials on a heating coil. For temperature distribution the heating coil is housed in a heat conducting sleeve. Accordingly, the welding temperature may be measured directly at the welding site.